Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$240.86	11.445%	$268.4264	$268.43	$268.45	$268.40
Purchase #2	$166.62	3.177%	$171.9135	$171.91	$171.90	$171.90
Purchase #3	$157.42	11.545%	$175.5941	$175.59	$175.60	$175.60
Purchase #4	$140.98	6.843%	$150.6273	$150.63	$150.65	$150.60
Purchase #5	$43.78	5.759%	$46.3013	$46.30	$46.30	$46.30
Purchase #6	$168.97	13.362%	$191.5478	$191.55	$191.55	$191.50
Purchase #7	$134.67	3.523%	$139.4144	$139.41	$139.40	$139.40
7 purchase totals =	$1,053.30		$1,143.8248	$1,143.82	$1,143.85	$1,143.70